Control of down-the-hole percussion drilling in the direction of optimizing the drilling process is today to a high degree entrusted to the operator. A skilled and experienced operator achieves over a time a feeling for the drilling process and is within limits capable of relatively good results when it comes to having a drilling rig perform well according to the circumstances. For that reason, a more skilled and experienced operator achieves normally better overall results when it comes to efficiency and total economy compared to a non-experienced operator.
Even the skilled and experienced operator can, however, not continuously over time regulate a drilling rig for best performance, in particular when the drill bit passes rock formations with different properties and during the varying conditions that prevail simply because of hole length and hole depth.
Also in respect of skilled and experienced operators, it can not be expected that all parameters associated with drilling can be adjusted for best performance during the drilling process.
When it comes to not so skilled and experienced operators, the same feel for the drilling process is likely not to have been achieved and the result is likely to be less efficient and in worse case damaging to the equipment including but not limited to the drill bit.
In order to monitor the drilling process, the operator may have access to drilling rate values, whereby drilled distance per time unit can be monitored. Further, the operator normally has access to parameter figures for fluid pressures, fluid flow rates and drill string rotator rotation rate. In order not to damage the drill bit or other pieces of the equipment during drilling, such parameters as i.a. feed force/weight on bit and hammer fluid pressure are subjected to limitations.